An ongoing goal of IC designers is the provision of a memory cell having a very small size, low power and current programming requirements, and long charge retention. A number of IC memory devices are known. A flash memory requires one transistor per memory cell and also requires high programming voltages. This type of non-volatile memory is not suitable for low-power, high-speed application. A ferroelectric-based RAM also requires a single transistor per memory cell, however, known FeRAMS have a relatively short charge retention time, on the order of nano-seconds. There are also problems associated with nano-scale structures when it is required to apply photoresist and to etch the structure. A MRAM requires high current to program data into the memory cell.
Fabrication of nano-scale (10−9 meters) ICs is limited by the resolution of the lithography portion of the fabrication process, which is approximately 0.1 μm (10−7 meters). E-beam lithography may able to define line width as narrow as 0.01 μm (10−8 meters), however, the through put is very slow. A manufacturing process having the reliability and throughput of conventional lithography and etching with nearly the resolution of E-beam lithography is therefore desirable.
Liu et al. Electrical-pulse-induced reversible resistance change effect in magnetoresistive films, Applied Physics Letters, Vol.76, #19, p.2749, May, 2000, describes use of colossal magnetoresistive (CMR) films in memory devices.